1. Technical Field
The present disclosure relates to a shift controller for a vehicle that sets a reference position of an actuator and more particularly to a shift controller that suppresses a decrease in accuracy for setting a reference position of an actuator due to a decrease in voltage supplied to the actuator at the time of performing reference position setting control.
2. Description of Related Art
In a vehicle including a shift switching unit configured to switch a shift position of the vehicle to one of a plurality of shift positions by driving an actuator which is supplied with power from a power supply and a rotation restricting element configured to restrict rotation of the actuator in a predetermined direction at a predetermined shift position of the plurality of shift positions, a so-called shift-by-wire shift controller that controls electrical switching of the shift position of the vehicle by driving the actuator based on a signal which is input in response to a driver's operation of a shift operating unit is known. A shift controller provided in a hybrid vehicle is disclosed as an example thereof in Japanese Patent No. 4248290. In Japanese Patent No. 4248290, the actuator that switches a shift position includes a pulse generator, the example, an encoder, that outputs a pulse signal corresponding to a degree of rotation of the actuator. The shift switching unit is controlled such that a target shift position is set by driving the actuator such that a count value of the pulse signal output from the encoder (an encoder count value) reaches a target encoder count value corresponding to each shift position. Only a degree of rotation (a rotation angle) of the actuator from a rotational position at a shift position at the time of starting the shift controller can be detected from the output signal of the encoder, and a reference position corresponding to a predetermined shift position, for example, a parking position (a P position), for controlling driving of the actuator needs to be set in order to appropriately control the shift position by driving the actuator.
Accordingly, when the shift controller is started, for example, when the vehicle is powered on, reference position setting control of setting the reference position of the actuator is performed. The reference position setting control causes the actuator to rotate to output a predetermined torque until rotation of the actuator is restricted by the rotation restricting element that restricts the rotation in a predetermined direction of the actuator disposed in the shift switching unit, detects a state in which the output signal of the actuator does not vary over a predetermined time, and sets a rotation stop position of the actuator in the state in which the output signal does not vary over the predetermined time as the reference position of the actuator corresponding to a predetermined shift position (for example, a P position or a non-P position). The reference position of the actuator is corrected, for example, by an amount of deflection or an angle of deflection of the rotation restricting element which is calculated based on an output torque of the actuator from a predetermined map. Accordingly, in order to set the reference position of the actuator with high accuracy, it is necessary to drive the actuator such that a predetermined torque is output therefrom in the reference position setting control.